1. Field of the Invention
The present invention relates to a turbo molecular pump, and particularly, to a turbo molecular pump capable of suppressing an electronic circuit section temperature rise in an electronic circuit section within a range required without losing airtight property thereof without a simple construction.
2. Description of the Related Art
As shown in Japanese Patent Application Laid-open No. 2000-240649 as an example in which a turbo molecular pump is constructed with a magnetic bearing of five-shafts control type, magnetic floating of a rotor is made by a high frequency motor and a magnetic bearing to perform high speed rotation support for a rotation blade in a non-contact manner, to thereby exhaust in a vacuum process gas of a semiconductor manufacturing apparatus.
The turbo molecular pump requires to be controlled based on individual parameters (such as specifying a machine model and various properties corresponding to the machine model) each of which undergoes adjustment. The above turbo molecular pump is provided with an electronic circuit section in its main body which is used for storing these control parameters. The electronic circuit section is composed of a semiconductor memory such as an EEP-ROM, an electronic component such as a semiconductor device used for accessing the semiconductor memory and a substrate for mounting the semiconductor memory.
This electronic circuit section is accommodated around the center portion of a base section by which the lower portion of the turbo molecular pump is constructed and is sealed by a bottom cover having airtight property. An exhaust port is formed in the base section.
Incidentally, in the turbo molecular pump, there is a problem in that saturation vapor pressure is exceeded by a discharged gas at the periphery of the exhaust port, and the like, with the result that products are likely to cause solidification or adhesion. In order to solve this problem as a general measure for a reaction product, the base section is heated by a heater or the like so that high temperature is constantly maintained therein.
Accordingly, the electronic circuit section of the base section is exposed to high temperature. Further, in some cases, the temperature of the electronic circuit section exceeds limitation temperature depending on variations of an exhaust load etc., to thereby break a storing means constituted by a semiconductor memory. With the semiconductor memory broken, when data disappearance or data change occurs, magnetic floating is not allowed to be conducted or the number of rotation becomes more than the maximum level to cause a danger.
The present invention is made in view of the above conventional problem, and an object of the present invention is therefore to provide a turbo molecular pump capable of suppressing temperature rise in an electronic circuit section within a range required, without losing airtight property thereof with a simple construction.
According to a turbo molecular pump of the present invention, the turbo molecular pump is characterized by comprising: a rotor blade; a magnetic bearing means for supporting the rotor blade with magnetic force and adjusting a position of the rotor blade with respect to its radius direction and/or its axial direction; a rotation driving means for conducting rotation driving of the rotor blade; a base section which is disposed at a lower portion of the magnetic bearing means and the rotation driving means and is provided with an exhaust port; a bottom cover equipping therein and for sealing the magnetic bearing means and the rotation driving means at a bottom portion of the base section; a semiconductor device disposed at an inner portion of the bottom cover; a cooling means for releasing to the outside heat of the semiconductor device; and a controlling means for controlling rotation of the magnetic bearing means and the rotation driving means.
The operation of the magnetic bearing means is controlled by the controlling means based on control parameters which are stored in the semiconductor device. The semiconductor device is provided with the cooling device, to thereby to release to the outside heat of the semiconductor device under an airtight state.
Thus, even when temperature rise occurs in the base section, temperature rise is suppressed in the semiconductor device temperature rise, resulting in that the function is maintained and the bearing can be controlled in a stable manner.
Also, according to the turbo molecular pump of the present invention, the turbo molecular pump is characterized in that the semiconductor device is provided with a temperature detecting means for detecting a temperature of the semiconductor device, and the controlling means includes an temperature abnormality detection section by which an alarm is output and an operation is stopped or either of the above processing is carried out, in accordance with a temperature detected through the temperature detecting means.
The above turbo molecular pump is equipped with the temperature detecting means and the temperature abnormality detection section in the semiconductor device, with the result that processing such as an alarm output is made in accordance with a state of the temperature of the semiconductor device. Accordingly, it becomes possible to safely deal with a trouble of the cooling means.
Further, according to the turbo molecular pump of the present invention, the turbo molecular pump is characterized in that the cooling means is disposed outside the semiconductor device so that the bottom cover is interposed there between.
The turbo molecular pump performs heat transfer through the bottom cover, and thus an airtight construction that is specially provided is not necessary and it is possible to cool the semiconductor device with a simple construction.
Still further, according to the turbo molecular pump of the present invention, the turbo molecular pump is characterized in that the cooling means is provided with a heat pipe disposed by piercing the bottom cover and/or the base section, and the semiconductor device is disposed on a heat receiving section of the heat pipe.
The semiconductor device is cooled directly by the heat pipe. Also, with a piercing portion of the heat pipe having a relatively small diameter, processing for making an airtight state can be easily conducted. Therefore, the simple construction enables the semiconductor device to be intensively cooled in an effective manner without losing airtight property.